In particular in the processing of plastics, it is often reasonable to provide two or several successive extruders, each of which performing individual processing steps. For example, when plastic material is used in the form of powder, inlet and melting of the powder can take place in a first extruder. Homogenizing and pressure build-up then takes place in a second, down-stream extruder. Successive extruder arrangements of the generic type are known for example from EP 1 005 411 B1, U.S. Pat. No. 3,261,056 and DE 2 304 088 A. In the plants of the generic type known from literature and practice, the connecting parts, which often have a weight of several tons, are hard to remove and re-insert, with removal of the connecting parts being indispensable for the screw shafts of the first extruder to be pulled out.
In practice, pulling out the screw shaft through the discharge zone is customary, because the other end is provided with the motor, coupling and transmission and pulling out the screw shaft there poses serious problems. The term ‘materials’ is to be understood as fundamentally free flowing materials that are treatable in screw-type extruding machines.